Study On The Mechanism And Equipment Of Dielectric Seed Separation

Dielectric separation is one of the important methods to separate seed. Thedielectric separator has the characteristics of simple structure, good adaptability,reliable separating effect, and classifying seeds according to the vigor differences thatother separation methods can not match. Although much attention is being paid ontheory and application both in China and abroad, the dielectric separator has not beenwidely used in seed production. This is because the principle of seed separation usingthe dielectric property is new and the researches in many aspects have not been donethoroughly. Therefore, the purpose of this study is to provide scientific basis fordielectric separator design and development through theoretical analysis andexperimental researches.Based on modeling the seed as a compound substance, the dielectric property ofthe seed was studied. Meanwhile, the factors affected the dielectric property of seedand the relationship between the dielectric property and seed vigor were bothanalyzed. By analyzing seed polarization in the electric field, the polarization forceformula of the seed was developed. The seed separation model on the bifilar-winding-cylinder was developed, which provided scientific basis for determining bothstructural and operational parameters for the dielectric separator.The previous model for electric field intensity of the bifilar-winding-cylinder wasdeveloped by means of simplifying the bifilar winding into two parallel infinitely longwires, and was widely applied. We developed a new electric field intensity model withthe similar method, but taking into account the electric field intensity produced byboth the neighboring electrodes and the other electrodes. Comparative analysisbetween the new model and the previous model was made. The new model was usedto examine the factors affecting the electric field intensity and the relationshipbetween electric field intensity and the parameters of the bifilar winding wasestablished, and measures to improve separating effect and to increase separatorperformance were presented. Since the model eliminates the weaknesses of the*previous model, it is more practical, more accurate in analyzing the effect ofparameters on the intensity of electric field and in designing the seed separator.Based on studies on electrode material and electrode construction, a newelectrode was designed, with aluminum as conductor and two layers of insulation.Polyethylene is used as inner insulation material to provide insulation and polyvinylchloride is used as the outer insulation material to protect polyethylene and provideinsulation as well. The minimum thickness for both the inner and outer insulationlayers was decided. Cylinders made from three electrodes of different sizes were usedto test the separation effect on wheat and millet seeds. "Whether small seeds or largeII2seeds, the cylinder with the smallest size electrode shows the best separation effect",which provides the scientific basis for accurate application of the electrode.On the basis of simpli1~ying the separating cylinder as a capacitor model withresistance, the capacitance formula for cylinders with single-insulation-layer electrodeand two-insulation-layer electrode were established respectively. Factors affecting thecapacitance were studied, energy of the electric field and power consumption of thecylinder were analyzed. Laboratory experiments were conducted to test and verify thetheory. The capacitance, energy, power consumption of the cylinder as a function ofseparating voltage and productivity were determined, which provided scientific basisfor the design of the transformer and power matching of seed separator.Based on the theoretical analysis and experimental studies, structural andoperationa...